Thanks for asking the query,
Your clinical history and symptoms suggest that you had developed a swelling under your tongue that can be a salivary gland
swelling, cystic lesion like ranula
, ulceration or some kind of infection arrising from the adjacent tooth of the jaw bone.
I would suggest you to visit to a Oral and Maxillofacial Surgeon and get the checkup done, take an OPG x-ray if needed, Exact daignosis will be made on visual and radiological examination.
I suggest you to quit the habit of smoking
Maintain a good oral hygiene
, use antiseptic mouthwash gargles twice daily.
Hope this helps out.